This invention relates to articles for laundry which facilitate arbitrary dispensing and can be conveniently used in practice with considerably relieved scattering or leak of the contents. More particularly, it relates to sheetlike detergent compositions for clothes.
Conventional powdery or granular detergents suffer from the problem of scattering. As modes for effectively solving this problem of scattering, there have been proposed one-pack type detergents (unit packed detergents) and sheetlike detergents composed of a water-soluble or water-insoluble film or nonwoven fabric impregnated with detergent components (JP-A2-228398, GB-B 2084176, etc.). In the latter mode, however, the detergent components are exposed on the surface and adhere to hands or containers. When a water-insoluble film or nonwoven fabric is used as the substrate to be impregnated, it should be disposed after using, thus resulting in poor handling properties. In this case, moreover, there arises another problem that the insoluble fiber would partly fall out from the substrate in the course of stirring in a washing machine and, after drying, remain on the surface of clothes. This trouble is serious particularly in the case of dark clothes, since the fiber residues on the surface of such clothes are highly conspicuous.
As an example of articles for laundry with the use of a water-insoluble substrate other than those of the impregnation type, U.S. Pat. No. 4,170,565 discloses a product composed of an active detergent sandwiched between nonwoven fabrics having a specific air permeability. In this patent, however, use is made of a tripolyphosphate as a builder in a builder-rich detergent for clothes and, moreover, the detergent has a high moisture content. As you know well, use of phosphate-containing detergents for clothes should be minimized, since they bring about a problem of eutrophication. However, a composition containing a tripolyphosphate as a builder and water each in an amount of 15% or more has a great advantage which cannot be achieved by any other builders. That is to say, such a composition is excellent in transportation properties of the active detergent raw material at a definite viscosity. When the tripolyphosphate is substituted merely by, for example, zeolite and a sufficient viscosity is imparted to the detergent raw material so as to form the sandwich structure, the transportation efficiency of the active detergent with a pump, etc. is seriously lowered. As a result, the coating onto the substrate or the processing of the active detergent into a sheet can be carried out only at an extremely low efficiency. Namely, it is highly difficult to produce phosphate-free articles according to the patent cited above. When a water-soluble sheet is used as a substitute for the water-insoluble nonwoven fabric with poor handling properties employed in this patent, it is needless to say that the moisture content should be largely reduced. In this case, therefore, a phosphate-free sheetlike detergent causing no residue can be hardly obtained.
U.S. Pat. No. 5,202,045 proposes another mode wherein an active detergent component and/or an active bleaching agent are packed into two parts of an S-shaped water-soluble nonwoven fabric. In this case, use is made of a builder-rich composition containing a tripolyphosphate and water each in an amount of 15% or more similar to the mode of U.S. Pat. No. 4,170,565 as stated above. That is to say, this patent discloses in practice no technique for providing detergents for clothes containing builders: in particular, zeolite; usable as a substitute for phosphates and having a low moisture content.
As a mode for solving one of these problems encountering in the prior art, JP-A 61-12796 proposes an article obtained by processing a non-powdery detergent composition containing a nonionic surfactant into a sheet and coating both surfaces thereof with a water-soluble film, etc. However, this patent discloses exclusively examples wherein water-soluble polymer compounds are mixed with bleaching agents and surfactants and the resultant mixtures are heat-molded into sheets. Therefore, the detergent components are partly exposed on the surfaces of the thus obtained sheets and adhere to hands or containers, similar to the articles of the impregnation type as described above. That is to say, this patent discloses no particular and effective technique for processing a detergent composition into a sheet and coating both surfaces of the sheet with a water-soluble film, etc.
Moreover, the compositions disclosed in the above patent are to be used as detergents on the assumption that other detergents are used together. Therefore, these compositions contain neither alkaline agents nor sequestering agents which are fundamental components of detergents for clothes. When such a composition is used alone, it is therefore impossible to achieve any sufficient detergency. Moreover, it is unfavorable from the viewpoints of convenience and economics to use them together with other detergents. It is also unfavorable to prepare these compositions by adding water-soluble polymer compounds such as polyvinyl alcohol. This is because, in this case, these water-soluble polymers come into contact with the alkaline agents at enlarged area and thus frequently undergo hydrolysis.
In most of detergents for clothes, surfactants, sequestering agents and alkaline agents are used in large amounts as fundamental components. It is very difficult to obtain a sandwich-type composition which is capable of carrying these active detergent components in large amounts.
Under these circumstances, it has been urgently required to develop a sheetlike detergent which contains a builder as a substitute for phosphates in a sufficient amount for achieving excellent detergency even though employed alone, is excellent in convenience and can carry relatively large amounts of active detergent components so as to prevent the contents from the scattering or leak. In the field of fiber softeners and bleaching agents, on the other hand, it has been also required to develop a sheetlike article for laundry which is freed from the scattering of powders, has a high compatibility with the environment, contains a fiber softening component or an active bleaching agent in a sufficient amount, has a high flexibility and can be completely dissolved in the step of laundry.